A Mooncup is a reusable menstrual cup made from medical-grade silicone that collects period blood rather than absorbing it. Launched in the United Kingdom in 2002, it was one of the first silicone menstrual cups to reach the commercial market successfully. You fold it, insert it like a tampon, and it sits inside the vaginal canal for up to 12 hours before you empty, rinse, and reinsert it. A single cup lasts for years, making it a popular alternative to disposable tampons and pads.
How a Menstrual Cup Works
Unlike tampons and pads, which absorb fluid, a Mooncup catches and collects it. Once inserted, the cup springs open and rests against the vaginal walls, forming a light suction seal that prevents leaks. Tiny holes near the rim help create and maintain that seal. Blood simply drips into the cup and stays there until you remove it.
To take it out, you pinch the base of the cup to break the seal, then gently pull it down. Trying to yank it out without breaking the suction first will be uncomfortable, so that pinch matters. You empty the contents into the toilet, rinse the cup with water, and reinsert it.
Capacity Compared to Tampons
Menstrual cups hold roughly twice the volume of a tampon. Most cups on the market hold between 10 and 38 ml of fluid depending on the brand and size, while a regular tampon absorbs about 5 ml and a super tampon around 10 to 12 ml. In practice, this means you can go much longer between changes. The maximum recommended wear time for a menstrual cup is 12 hours, though on heavier days you may need to empty it more often.
Choosing the Right Size
Mooncup and most other cup brands offer two sizes, and the guidelines are straightforward. The smaller size is generally designed for people under 30 who have never been pregnant or given birth. The larger size is recommended for those over 30, or anyone who has carried a pregnancy to full term or delivered a child vaginally. The difference comes down to changes in pelvic floor tone and vaginal width that occur with age and childbirth.
If you’re between categories or unsure, cervix height can also help. During your period, you can reach inside to feel how high or low your cervix sits. A low cervix works better with a shorter cup, while a high cervix gives you room for a longer one. Some trial and error is normal when starting out.
How to Insert a Mooncup
The cup needs to be folded before insertion to make it narrow enough to go in comfortably. The two most common folds are the C-fold and the punch-down fold. For the C-fold, you flatten the cup by pinching it in half, then fold it in half again so the rim forms a C or U shape. For the punch-down fold, you press one edge of the rim down toward the base of the cup with your thumb, creating a narrow pointed tip that’s easier to insert.
Once inside, the cup should pop open on its own. If it doesn’t fully open or feels off, rotating it slightly with your fingers usually helps it settle into place. You shouldn’t feel the cup once it’s positioned correctly. If you do, it may be sitting too low or hasn’t opened all the way.
Cleaning and Sterilization
During your period, rinsing the cup with water each time you empty it is enough. If you don’t have access to a sink (like in a public restroom), wiping it with toilet paper and reinserting it works in a pinch, with a proper rinse at the next opportunity.
Between cycles, the cup needs to be sterilized. The standard method is to boil it in water for a few minutes, then let it cool and dry completely before storing it. Some brands sell microwave-safe sterilizing containers that let you boil the cup in the microwave for 3 to 4 minutes. Keeping the tiny rim holes clear of buildup is important, since clogged holes can weaken the suction seal and lead to leaks.
Safety and Toxic Shock Syndrome
Toxic shock syndrome (TSS) is rare but possible with any internal menstrual product, including cups. A lab study published in Applied and Environmental Microbiology found that menstrual cups are not inherently safer than tampons when it comes to TSS risk. The researchers observed that the bacteria responsible for TSS actually grew slightly more in the presence of cups than tampons, likely because cups introduce more air into the vaginal canal, and oxygen fuels bacterial growth and toxin production.
The study also found that larger cups were associated with higher levels of toxin production, suggesting that using the smallest cup that works for your flow is a reasonable precaution. Another finding: a significant amount of bacterial biofilm remained on cups even after rinsing with water three times. The researchers recommended boiling the cup between uses, ideally rotating between two cups so one can be sterilized while the other is in use.
None of this means cups are dangerous. TSS from any menstrual product is extremely rare. But the same basic rules apply as with tampons: don’t leave it in longer than 12 hours, wash your hands before insertion and removal, and sterilize the cup properly between cycles.
Why People Switch to Cups
The practical appeal is mostly about convenience and cost. A single Mooncup costs roughly the equivalent of a few months’ worth of tampons, and it lasts for years. Over a decade, the savings add up significantly. There’s also the waste reduction: the average menstruating person uses thousands of disposable products over a lifetime, and a reusable cup eliminates nearly all of that.
Comfort is the other factor. Because silicone doesn’t absorb moisture the way cotton does, cups don’t cause the dryness that some people experience with tampons, particularly on lighter flow days. The silicone properties of the Mooncup specifically were a key reason the product succeeded commercially where earlier rubber and latex cups hadn’t gained traction. Medical-grade silicone is flexible, hypoallergenic, and holds up to repeated sterilization without degrading.
There is a learning curve. Most people need two or three cycles to get comfortable with insertion, removal, and finding the right fold. Removal in particular can feel awkward at first, especially if you forget to break the seal before pulling. But once the technique clicks, most users find the cup less disruptive to daily life than disposable products, largely because of the longer wear time and reduced risk of running out of supplies.